Ortho-phenylphenol (OPP) has been used as a germicide, disinfectant, citrus fruit preservative and dye intermediate.
OPP has been synthesized by several methods. The methods have either used expensive reactants or resulted in low OPP yields as a result of low conversion or low selectivity. The percent conversion of a reactant is 100 times the ratio of moles of the reactant converted into product or by-product over the initial moles of the reactant. Percent selectivity is 100 times the ratio of the moles of a reactant converted into a desired product over the moles of said reactant converted into product or by-product.
OPP has been formed by reacting sodium phenylate with diphenyl oxide in an ethereal solvent (Luttringhaus in Annelen 542 (1939) 241). The reaction yields about 48 percent OPP.
Basic hydrolysis of ortho-chlorobiphenyl using a cupric oxide catalyst results in an 83 percent OPP yield. However, because the typical route to ortho-chlorobiphenyl, chlorination of biphenyl (e.g., U.S. Pat. No. 1,925,367) has poor ortho selectivity, the overall yield of OPP from the biphenyl is significantly less than 83 percent.
Catalytic hydrogenation of dibenzofuran yields 80 percent phenylphenol conversion with 90 percent of the phenylphenol being OPP (Japanese Patent No. 58-180,448). The catalyst, 0.5-1 percent platinum on alumina, has been reported to suffer from a short lifetime.
Self condensation of cyclohexanone to a mixture of cyclohexenyl cyclohexanone and cyclohexylidenyl cyclohexanone followed by catalytic dehydrogenation to OPP is known. The self condensation reaction conversion to the above mixture is 50 percent and the catalytic yield of OPP is greater than 98 percent. The OPP overall conversion is, of course, the product of the two reactions and it is important to note that cyclohexanone is an expensive reactant.
Therefore, it would be desirable to provide a cost effective high yield method to produce ortho-phenylphenol.